全文获取类型
收费全文 | 31801篇 |
免费 | 3967篇 |
国内免费 | 425篇 |
专业分类
36193篇 |
出版年
2023年 | 137篇 |
2022年 | 275篇 |
2021年 | 548篇 |
2020年 | 399篇 |
2019年 | 439篇 |
2018年 | 609篇 |
2017年 | 534篇 |
2016年 | 786篇 |
2015年 | 1103篇 |
2014年 | 1194篇 |
2013年 | 1434篇 |
2012年 | 1647篇 |
2011年 | 1722篇 |
2010年 | 1036篇 |
2009年 | 1016篇 |
2008年 | 1313篇 |
2007年 | 1220篇 |
2006年 | 1136篇 |
2005年 | 1025篇 |
2004年 | 1013篇 |
2003年 | 940篇 |
2002年 | 884篇 |
2001年 | 2665篇 |
2000年 | 2445篇 |
1999年 | 1782篇 |
1998年 | 572篇 |
1997年 | 540篇 |
1996年 | 481篇 |
1995年 | 472篇 |
1994年 | 356篇 |
1993年 | 308篇 |
1992年 | 882篇 |
1991年 | 778篇 |
1990年 | 636篇 |
1989年 | 548篇 |
1988年 | 441篇 |
1987年 | 369篇 |
1986年 | 288篇 |
1985年 | 268篇 |
1984年 | 192篇 |
1983年 | 153篇 |
1982年 | 103篇 |
1981年 | 106篇 |
1980年 | 89篇 |
1979年 | 100篇 |
1978年 | 99篇 |
1977年 | 86篇 |
1975年 | 68篇 |
1974年 | 73篇 |
1973年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Rafael L. X. Consani Mariana R. Carmignani Marcelo F. Mesquita Lourenço Correr‐Sobrinho Ricardo D. Guiraldo 《Gerodontology》2010,27(3):236-242
doi:10.1111/j.1741‐2358.2009.00333.x Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin Objective: The purpose of this study was to verify the effect of microwave treatment on the shear bond strength of commercial types of teeth to acrylic resin, when the glossy ridge laps were unmodified (groups 1 and 5), bur abraded (groups 2 and 6), bur grooved (groups 3 and 7) or etched by monomer (groups 4 and 8). Background: Controversial findings have shown that mechanical or chemical changes in ridge‐lap surface of the tooth increase or decrease the bond strength between tooth and acrylic resin, and the microwave disinfection may cause different changes on this bond strength. Materials and methods: Eighty specimens (n = 10) were made with the acrylic resin bonded to tooth glossy ridge lap, polymerised in water at 74°C for 9 h, and deflasked after flask cooling. Specimens of the groups 5, 6, 7 and 8 were individually immersed in 150 ml of water and submitted to microwave treatment in an oven at 650 W for 3 min. Control specimens (groups 1, 2, 3 and 4) were not microwave treated. Shear bond strength test was performed in an Instron machine with a cross‐speed of 1 mm/min. Collected data were submitted to anova and Tukey’s test (α = 0.05). Results: Microwave treatment decreased the shear bond strength values of the tooth/resin bond. In the microwaved and non‐microwaved procedures, mechanical retention improved the shear bond strength when compared with the control and monomer treatments. Conclusion: Shear bond strength of the tooth/resin bond was influenced by the microwave treatment and different commercial teeth association, and was lower for the Biotone tooth. 相似文献
43.
44.
G. Matthew Hebdon Harry Le Vine Naji E. Sahyoun Claus J. Schmitges Pedro Cuatrecasas 《Life sciences》1980,26(17):1385-1396
3T3C2 mouse fibroblasts rendered permeable to (α?32P)NAD+ show cholera toxin-dependent labeling of a 45,000 m.w. protein and of a doublet of polypeptides around 52,000 m.w. These same bands are ADP-ribosylated in broken cells. Membranes prepared from pigeon erythrocytes pretreated with choleragen show a decrease in subsequent cholera toxin-specific ADP-ribosylation of a 43,000 m.w. polypeptide. Both whole cell and broken cell adenylate cyclase activation and toxin-specific ADP-ribosylation are reversed specifically by low pH and high concentrations of toxin and nicotinamide in all systems. Thus ADP-ribosylation appears to be relevant to the molecular action of choleragen in whole cells as well as in broken cells. 相似文献
45.
46.
47.
E Gluckman J Lotsberg A Devergie X M Zhao R Melo M Gomez-Morales M C Mazeron Y Pérol 《Revue fran?aise de transfusion et immuno-hématologie》1984,27(3):391-396
In a double-bind controlled study, oral Acyclovir has been compared to a placebo in a series of 39 consecutive patients undergoing bone marrow transplantation. A dose of 200 mg was given every 6 h from day 8 to day 35 after transplantation. Pharmacokinetic studies have shown the good absorption of the drug despite intestinal damage related to chemoradiotherapy or gut graft-versus-host disease (GVHD), there was no sign of toxicity. The protection against herpes simplex virus (HSV) infection was complete in the treated group when compared to the control group even in patients with high anti-HSV antibody titres. The same protection was observed against cytomegalovirus (CMV) infection. The incidence of HSV and CMV was the same in both groups after treatment ended. This study confirms the efficacy of Acyclovir against HSV infection and possibly against CMV infection when it is given prophylactically after bone marrow transplantation. 相似文献
48.
Unpublished portions of the synthesis of a phosphinate-phosphonate diether analog of CDPdiacylglycerol are reported. The liponucleotide analog was found to be a very powerful inhibitor of platelet PI synthetase; kinetic data suggest a competitive inhibition mechanism. The structural specificity of CDPdiacylglycerol for liponucleotide-mediated biosynthetic reactions is discussed. 相似文献
49.
50.
Chap T. Le 《Biometrical journal. Biometrische Zeitschrift》1988,30(1):87-92
The distribution-free test against ordered alternatives proposed by Jonckheere (1954) is based on the Kendall's rank correlation coefficient τ. A new rank test is proposed and illustrated with a numerical example. The proposed test is based on Spearman's σ and has similar functional structure as the Kruskal-Wallis test. A useful by-product is a test for departure from a trend. 相似文献